The main objective of this study is to study the cause of muscle wasting with age and to determine whether exercise training can reduce the muscle loss. This study was started at the University of Vermont in Burlington and continued by Dr. Nair at Mayo. There is a decline of muscle mass with advancing age. This muscle wasting with aging causes physical disabilities including a decrease in strength and tendency to fall. At present, the cause of muscle wasting with aging is not known. Methods of measuring the body's ability to make muscle protein have been developed. In the current project, the objective is to assess the ability of the body to make muscle protein in healthy subjects of ages ranging from 20-80 years. The effect of age, physical activity, and exercise training on the body's ability to make muscle protein is being assessed. The study has been closed to new participants since March 1995. Analysis of the samples and data will continue. To date, over 30 abstracts, publications, and presentations have resulted from this work.